Urea Nitrate Research Articles

H2S induced in-situ formation of recyclable metal sulfide-based sorbent for elemental mercury sequestration in natural gas

Enlightened by the phenomenon that hydrogen sulfide (H2S) can readily decompose on metal oxides to generate sulfide species and the obtained metal sulfides are generally adopted as Hg-affine ligands for Hg0 capture, a urea modified copper oxide (U-CuO) was prepared via high-temperature calcination of the mixture of urea and copper nitrate for Hg0 removal in natural gas containing H2S. Benefitted from the decomposition of urea and the release of gaseous decomposition products, the as-synthesized U-CuO was enriched with abundant base sites and lattice oxygen, and characterized with developed textural features, which facilitates the diffusion and adsorption of H2S and subsequent sequestration of Hg0. The Hg0 adsorption capacity and uptake rate of U-CuO under simulated natural gas (N2 + 500 ppm H2S+8% H2O) reached as high as 134.06 mg g−1 and 58.32 μg g−1 min−1, respectively, which largely surpassed those of most CuS-based sorbents for Hg0 immobilization. Besides, U-CuO sorbent also exhibited satisfactory recyclability only through simple thermal treatment, the Hg0 removal efficiency of U-CuO maintained above 97 % even after ten adsorption-regeneration rounds. This preparation strategy not only provides valuable hints to guide the design and synthesis of Hg0 sorbents used for natural gas containing H2S but also inspires further investigation for the cost-effective performance enhancement of Hg0 sorbents.

One-step high-efficiency microwave synthesis of N-doped bamboo biochar for tetracycline degradation

N-doped bamboo biochar (NBB) was successfully synthesized through one-step, rapid pyrolysis (e.g., 10 min) using urea and urea nitrate impregnated bamboo particles exposed to low power (e.g., 460 W) microwave radiation. NBB-460 exhibited high specific surface area of 876.1 m2/g and outstanding catalytic performance for tetracycline hydrochloride (TCH) degradation. The TCH degradation efficiency reached to 94.3 % with the optimized catalytic condition (i.e., 0.2 g/L NBB-460, 3 mM PMS, 50 mg/L TCH, 25 ℃, without pH regulation). The density functional theory calculation showed that the graphitic nitrogen and pyridinic nitrogen of NBB-460 served as active sites for peroxymonosulfate activation and TCH degradation. The quenching test, electron paramagnetic resonance spectra, and electrochemical measurements indicated that tetracycline hydrochloride underwent degradation via radical (O2•−), non-radical (1O2) pathways, and surface electron transfer. This study introduces an energy-efficient and time-effective method for converting biomass to N-doped biochar as highly efficient peroxymonosulfate activator for environmental applications.

THE EFFECT OF DIVIDED TOP-DRESSING APPLICATIONS OF DIFFERENT NITROGEN FERTILIZERS ON GRAIN YIELD AND QUALITY TRAITS IN BREAD WHEAT (Triticum aestivum L.)

This study was carried out to determine the effect of different divided top-dressing applications of different nitrogen fertilizers on grain yield and quality traits of four bread wheat varieties (Selimiye, Esperia, Gelibolu and Rumeli). The experiment was conducted in a randomized split-plot design with 3 replicates during the 2017 and 2018 seasons. In the experiment, varieties were allotted as main plots and top-dressing applications were allotted as subplots. Five different pure nitrogen (N) top-dressing applications were done in the form of urea and calcium ammonium nitrate (CAN) at the beginning of tillering, the end of tillering, the beginning of stem elongation and the end of stem elongation stages. Grain yield, thousand kernel weight, test weight, protein content, wet gluten content, gluten index, Zeleny sedimentation value and delayed sedimentation value were investigated in the study. Gelibolu variety for grain yield, Rumeli and Esperia varieties for grain quality were prominent. The considering the ease of application for grain yield and quality, 2nd application (80 kg ha-1 pure N in the form of urea at the beginning of tillering, 40 kg ha-1 pure N in the form of urea at the beginning of stem elongation) can be proposed in the years when April and May rainfalls are sufficient, and 3rd application ( 40 kg ha-1 pure N in the form of urea at the beginning of tillering, 40 kg ha-1 pure N in the form of urea at the end of tillering, 40 kg ha-1 pure N in the form of CAN at the beginning of stem elongation) can be proposed in the years when April and May rainfalls are insufficient.

Mowing aggravates the adverse effects of nitrogen addition on soil acid neutralizing capacity in a meadow steppe

Soil acidification induced by reactive nitrogen (N) inputs is a major environmental issue in grasslands, as it lowers the acid neutralizing capacity (ANC). The specific impacts of different N compound forms on ANC remain unclear. Grassland management practices like mowing and grazing can remove a considerable amount of soil N and other nutrients, potentially mitigating soil acidification by removing N from the ecosystem or aggravating it by removing base cations. However, empirical evidence regarding the joint effects of adding different forms of N compounds and mowing on ANC changes in different-sized soil aggregates is still lacking. This study aimed to address this knowledge gap by examining the effects of three N compounds (urea, ammonium nitrate, and ammonium sulfate) combined with mowing (mown vs. unmown) on soil ANC in different soil aggregate sizes (>2000 μm, 250–2000 μm, and <250 μm) through a 6-year field experiment in Inner Mongolia grasslands. We found that the average decline in soil ANC caused by ammonium sulfate (AS) addition (−78.9%) was much greater than that by urea (−25.0%) and ammonium nitrate (AN) (−52.1%) as compared to control. This decline was attributed to increased proton (H+) release from nitrification and the leaching of exchangeable Ca2+ and Mg2+. Mowing aggravated the adverse effects of urea and AN on ANC, primarily due to the reduction in soil organic matter (SOM) contents and the removal of exchangeable Ca2+, K+, and Na + via plant biomass harvest. This pattern was consistent across all aggregate fractions. The lack of variation in soil ANC among different soil aggregate fractions is likely due to the contrasting trend in the distribution of exchangeable Ca2+ and Mg2+. Specifically, the concentration of exchangeable Ca2+ increased with increasing aggregate size, while the opposite was true for that of exchangeable Mg2+. These findings underscore the importance of considering the forms of N compounds when assessing the declines of ANC induced by N inputs, which also calls for an urgent need to reduce N emissions to ensure the sustainable development of the meadow ecosystems.

Effects of Rainfall Intensity and Slope on Infiltration Rate, Soil Losses, Runoff and Nitrogen Leaching from Different Nitrogen Sources with a Rainfall Simulator

The combined effects of slope gradient, rainfall intensity, and nitrogen fertilizer source on infiltration, runoff, soil loss, and nitrogen (N) leaching in agricultural areas are not thoroughly understood, despite their critical importance in sustainable agriculture. Previous studies have focused on these factors individually, leaving a significant gap in knowledge regarding their synergistic impact. Investigating the interplay between slope gradients, rainfall intensities, and N fertilizer sources is vital to developing effective soil and water conservation strategies and implementing sustainable agricultural practices. This study is comprised of two experiments. Experiment 1 was designed as a 3 × 2 × 3 factorial arrangement, incorporating three levels of rainfall intensity (RI) (45, 70, and 100 mm/h), two slope gradients (5 and 8°), and three soil types (sandy loam, silt loam, and clay loam), aimed at assessing runoff, infiltration, and soil loss. Experiment 2, laid out as 3 × 2 × 3 × 3 factorial, expanded on this, adding N fertilizer source (urea, CaCN2, and limestone ammonium nitrate (LAN) at 130 kg/ha N) and assessing N leaching alongside the previous metrics. Both experiments used a rotating disc rainfall simulator and were replicated four times. Results revealed that steeper slopes (8°) led to increased runoff and soil loss, impeding infiltration, while gentler slopes (5°) facilitated greater infiltration and minimized soil loss. Rainfall intensity played a significant role, with 70 mm/h/5° combinations promoting higher infiltration rates (48.14 mm/h) and 100 mm/h/8° resulting in lower rates (37.07 mm/h for sandy loam and silt loam, 26.09 mm/h for clay loam). Nitrogen leaching varied based on N source; urea at 130 kg/ha N led to higher losses (7.2% in sandy loam, 6.9% in silt loam, 6.5% in clay loam), followed by LAN (6.9% in sandy loam, 6.7% in silt loam, 6.3% in clay loam) while CaCN2 at the same rate resulted in lower N losses (6.4% in sandy soil, 4.4% in silt loam, 4.2% in clay soil). This research highlights the critical need to consider both slope gradient and rainfall intensity in conjunction with appropriate nitrogen fertilizer sources when developing strategies to mitigate soil erosion and nutrient loss in agricultural settings.

Application of Urea and Ammonium Nitrate Solution with Potassium Thiosulfate as a Factor Determining Macroelement Contents in Plants

The following research hypotheses were established in this study: the applied urea and ammonium nitrate solution with potassium thiosulfate (UAN-KTS) has a positive effect on the chemical composition of spring wheat, spring rape and maize; fertilization with nitrogen, potassium and sulfur increases their contents in the usable parts of plants; the forms of applied fertilizers reduce the antagonistic effect of nitrogen and potassium on the content of other elements in plants. Two doses of nitrogen (N 1—optimal dose of nitrogen for a plant species; N 2—25% lower dose of nitrogen) and different ratios of N:K:S elements (N:K:S—without K and S; N:K1:S1—a narrowed ratio; N:K2:S2—the optimal ratio; N:K3:S3—an expanded ratio) were applied. The experiment was carried out on two soils of different quality. The improved soil quality resulted in a significant increase in the calcium (as opposed to magnesium) content of the three crops, in the nitrogen and sulfate–sulfur (VI) content of spring wheat grain and spring rapeseed, and in the phosphorus content of spring rapeseed and maize aerial parts. Reducing the dose (N 2) had a negative effect on the nitrogen content of spring wheat and on the sulfate–sulfur (VI) content of spring rape, maize and especially spring wheat. Increasing the N:K:S ratio had a small but usually antagonistic effect on the nitrogen content of all plant species, but a synergistic one on the potassium content of spring wheat, maize and partly of spring rape, and especially on the content of sulfate–sulfur (VI) in the crops. The effect of type of soil and fertilizers with different N:K:S ratios on the content of other macronutrients was related to plant species. The new fertilizer with the N:K2:S2 ratio had the greatest effect on the content of the tested macronutrients in spring wheat, spring rape and maize. In order to confirm the obtained relationships, it seems justified to carry out field experiments and studies with other plant species.

Highly Sensitive, Easy-to-Use, One-Step Detection of Peroxide-, Nitrate- and Chlorate-Based Explosives with Electron-Rich Ni Porphyrins.

Homemade explosives, such as peroxides, nitrates, and chlorates, are increasingly abused by terrorists, criminals, and amateur chemists. The starting materials are easily accessible and instructions on how to make the explosives are described on the Internet. Safety considerations raise the need to detect these substances quickly and in low concentrations using simple methods. Conventional methods for the detection of these substances require sophisticated, electrically operated, analytical equipment. The simpler chemical detection methods are multistep and require several chemicals. We have developed a simple, one-step method that works similarly to a pH test strip in terms of handling. The analytical reaction is based on an acid-catalyzed oxidation of an electron-rich porphyrin to an unusually stable radical cation and dication. The detection limit for the peroxide-based explosive triacetone triperoxide (TATP), which is very frequently used by terrorists, is 40 ng and thus low enough to detect the substance without direct contact via the gas phase. It is sufficient to bring the stick close to the substance to observe a color change from red to green. Nitrates and chlorates, such as ammonium nitrate, urea nitrate, or potassium chlorate, are detected by direct contact with a sensitivity of 85-350 ng. A color change from red to dark brown is observed. The test thus detects all homemade explosives and distinguishes between the extremely impact-, shock-, and friction-sensitive peroxides and the less sensitive nitrates and chlorates by color change of a simple test strip.

One pot synthesis of multi-functional B doped g-C3N4-praseodymium oxide nanocomposites for colorimetric detection of Hg2+ ion and solar photocatalytic removal of toxic water pollutants

A novel praseodymium oxide-boron co-doped graphitic carbon nitride composite was synthesized via one-step solid-state thermal condensation of urea, orthoboric acid and praseodymium nitrate precursors. The prepared composites were characterized by various methods. All the prepared composites demonstrated multi-functional activities towards peroxidase-mimetic based colorimetric detection of Hg2+ ions and superior photocatalytic efficiency towards photodegradation of textile colorants, photoreduction of hexavalent chromium and nitro aromatics like para-nitro phenol (PNP) and para-nitro aniline (PNA). The superior photocatalytic activity can be attributed to the formation of type II heterojunction which facilitates charge separation and increases the lifetime of photogenerated charge pairs. As evident from the scavenger studies, these charge pairs are involved in the formation of superoxide and hydroxyl radicals. The superior activity of the optimum composite can be attributed to the porous flaky morphology, decreased optical band gap, heterojunction mediated charge separation, and praseodymium oxide's conductive nature. A linear range of about 0.25–800 nM of Hg2+ ions can be detected with a limit of detection (LOD) of 42.4 nM using the colorimetric strategy. The as-synthesized composite is thus a unique, efficient, economically viable, and excellent candidate for detecting and degrading various hazardous water pollutants.

Influence of the Nitrogen Fertilization on the Yield, Biometric Characteristics and Chemical Composition of Stevia rebaudiana Bertoni Grown in Poland.

Stevia rebaudiana Bertoni is a plant native to South America that has gathered much interest in recent decades thanks to diterpene glycosides, called steviosides, which it produces. These compounds are characterised by their sweetness, which is 250-300 times higher than saccharose, and they contain almost no caloric value. Stevia is currently also grown outside the South American continent, in various countries characterised by warm weather. This research aimed to determine whether it is viable to grow Stevia rebaudiana plants in Poland, a country characterised by a cooler climate than the native regions for stevia plants. Additionally, the impact of adding various dosages and forms of nitrogen fertiliser was analysed. It was determined that Stevia rebaudiana grown in Poland is characterised by a rather low concentration of steviosides, although proper nitrogen fertilisation can improve various characteristics of the grown plants. The addition of 100 kg or 150 kg of nitrogen per hectare of the field in the form of urea or ammonium nitrate increased the yield of the stevia plants. The stevioside content can be increased by applying fertilisation using 100 kg or 150 kg of nitrogen per hectare in the form of ammonium sulfate. The total yield of the stevia plants grown in Poland was lower than the yield typically recorded in warmer countries, and the low concentration of steviosides in the plant suggests that more research about growing Stevia rebaudiana in Poland would be needed to develop profitable methods of stevia cultivation.

Innovative Fertiliser Based on Urea and Ammonium Nitrate Solution with Potassium Thiosulphate as a Crucial Factor in Shaping Plant Yield and Its Parameters

In the cultivation of crops in recent times, in addition to taking care of the balanced supply of nutrients to plants and the protection of soil resources, it is also important to take into account the non-productive factor by implementing production systems based on balanced fertilisation. The aim of this study was to demonstrate the effect of soil kind and the application of a new fertiliser based on a urea and ammonium nitrate solution with potassium thiosulphate (UAN-KTS) on the yielding and biometric characteristics of spring wheat, spring rape, and maize to determine the optimal N:K:S ratio. An increase in the soil kind increased the weight of 1000 spring rape seeds, the yield of maize fresh matter, a reduction in the height of spring wheat and maize plants, a reduction in the yield of spring wheat grains and straw, and the yield of the fresh and dry matter of spring rape straw. A higher nitrogen dose promoted the growth of spring rape at the later growing stage and maize and had a positive effect on the yield of spring wheat grains and straw, spring rape seeds and straw, and the above-ground parts of maize. The application of potassium fertilisers caused a significant increase in the spring rape plant height, an increase in the yield of spring wheat grains and straw and spring rape seeds and straw, the above-ground parts of maize, a reduction in the plant height at the beginning of the spring wheat growing period, and a reduction in the weight of 1000 spring rape seeds (only on the soil with rich quality). The fertiliser with the N:K2:S2 ratio had a particularly favourable effect on the yielding of spring wheat. In the cultivation of maize, the same effect was most often obtained under the influence of fertiliser in the ratio of N:K1:S1 on the weaker soil fertilised at the same time as a higher dose of nitrogen (N 1) and N:K2:S2 (in other cases). In the case of spring rape, generally, fertiliser with N:K1:S1 was the strongest, although, in some objects, a higher yield was achieved under the influence of N:K2:S2. The existence of statistically confirmed correlations (expressed as the percentage of the variability observed) between the soil kind and the fertilisers applied and the yielding and biometric characteristics of the plants were observed.

CO2 emission and physiological aspects of sugarcane ratoon as interactive functions of nitrogen and silicon applications

Sugarcane is the primary renewable energy source in Brazil, necessitating efficient and sustainable production practices. This study assessed the impact of nitrogen sources and their combination of silicon as foliar application on carbon dioxide (CO2) emissions and physiological characteristics of sugarcane cultivated in tropical environment. The experiment was conducted using the second sugarcane ratoon (variety CTC-04), as 2x5 factorial design, with two sources of N-fertilizer (urea and calcium ammonium nitrate - CAN, association with DMPSA − 3,4-dimetilprirazol succínico, nitrification inhibitor) and different silicon concentrations such as 0, 150, 300, 450, and 600 g ha−1. Photosynthetic leaf gas exchange, water use efficiency, pigments, CO2 emissions (ECO2), ammonium and nitrate levels in the soil were observed. The results were subjected to analysis of variance using the F test along with polynomial regression and mean comparison tests. Using urea as a source of nitrogen, there was an increase in internal CO2 concentration of the plants by 19% in relation to treatment with calcium ammonium nitrate association with DMPSA (CAN + DMPSA). Nevertheless, urea increased ECO2 emissions into the atmosphere by up to 15.3% higher compared to CAN + DMPSA application. Foliar application of Si (300 g ha−1) reduced plant transpiration rate (21%), irrespective the source of N-fertilizer utilized. Thus, it is concluded that the use of calcium ammonium nitrate associated with a nitrification inhibitor is an interesting strategy for reducing CO2 emissions, as well as Si is capable of reducing the plant’s transpiration rates, making it efficient in the use of water.

Optimization of an Alternative Culture Medium for Phycocyanin Production from Arthrospira platensis under Laboratory Conditions.

Arthrospira platensis, known as spirulina, is a cyanobacterium with multiple nutritional benefits, as it contains substantial amounts of proteins, fatty acids, and pigments. However, the production of this microalga has faced significant challenges, primarily related to the cost and composition of the required culture medium for its optimal growth. This study focused on optimizing two nitrogen sources (urea and potassium nitrate) to maximize the growth of A. platensis and the production of phycocyanin, a photosynthetic pigment of significant commercial value. Optimization was performed using the response surface methodology (RSM) with a central composite design (CCD). Analysis of variance (ANOVA) was employed to validate the model, which revealed that the different concentrations of urea were statistically significant (p < 0.05) for biomass and phycocyanin production. However, potassium nitrate (KNO3) showed no significant influence (p > 0.05) on the response variables. The RSM analysis indicated that the optimal concentrations of KNO3 and urea to maximize the response variables were 3.5 g L-1 and 0.098 g L-1, respectively. This study offers valuable perspectives for the efficient production of A. platensis while reducing production costs for its cultivation on a larger scale.

A novel Z‐scheme heterojunction g‐C3N4/g‐C3N4/Pr6O11 for efficient visible‐light photocatalytic degradation of sulfonamide

Photocatalytic technology, as an environmentally friendly technology, has a great application promise in the treatment of environmental pollutants caused by residual pharmaceuticals emissions. The Z‐scheme heterojunction of g‐C3N4/g‐C3N4/Pr6O11 (Pr/CN) was successfully prepared by employing melamine, urea, and praseodymium nitrate as co‐precursors. The structure composition and photoelectrochemical properties were characterized by XRD, XPS, EDS, SEM, FETEM, UV–Vis, EIS, photocurrent, and PL analyses. The optimized 5wt%Pr/CN heterojunction degrade 98% of SCP, 85% of SMM, and 87% of SDM, respectively. Taking SCP as an example, the degradation rate is 8 and 11.2 times higher than that of the g‐C3N4/g‐C3N4 homojunction and g‐C3N4, respectively. The remarkable photocatalytic efficiency of Pr/CN heterojunction could be ascribed to enhanced visible light absorption and enhanced migration and separation of photogenerated charge carriers. Furthermore, the degradation products and degradation pathways of SCP and SMM were established by HPLC‐MS/MS analysis. In addition, the toxicity of the intermediate was evaluated with quantitative structure–activity relationship (QSAR) prediction and the biocompatibility of sulfonamide‐degrading solution over the Pr/CN photocatalyst was verified by the growth of wheat seeds.

Rapid Quantification of Ammonium Nitrate and Urea Nitrate Using Liquid Chromatography-High-Resolution Orbitrap Mass Spectrometry.

Resolution and sensitivity improvements in mass spectrometry technology have enabled renewed attempts at solving challenging analytical issues. One such issue involves the analysis of energetic ionic species. Energetic ionic species make up an important class of chemical materials, and a more robust and versatile analytical platform would provide tremendous value to the analytical community. Initial attempts at quantification of energetic ionic species employed high-resolution time-of-flight measurements with crown ether (CE) complexation and flow injection analysis (FIA). In this investigation, ammonium nitrate (AN) and urea nitrate (UN) in the presence of a crown ether complexation agent were explored by using high-resolution orbitrap mass spectrometry. Product ion scans of these signature complexes reveal positive identification of these energetic ionic species. Finally, quantification was demonstrated for both flow injection and liquid chromatography-mass spectrometry (LC-MS) analysis, suggesting the capability for routine and rapid analysis of these energetic ionic materials.

Stoichiometry of arable black soil on the Ukrainian Western forest steppe

ABSTRACT Luvic Greyzemic Phaeozems have been farmed for centuries in Western Ukraine. We investigate their stocks of major nutrients and stoichiometry under arable crops receiving conventional NPK fertilisation and an unfertilised control. Total carbon stocks increase only with parallel increases in total N, P, Ca and Mg. Likewise, total N increases along with parallel increases in total Ca and Mg, P and Ca, P and C. Under winter barley, application of the background fertilisation (N23P60K60) + N97 (urea) before sowing, with or without nitrapyrin as a nitrogen stabiliser, improved the status of C, N, Ca and Mg to P in the 0–20 cm soil layer. The best ratio of total C, N, Ca and Mg to P and the best C:N, C:P, N:P, and Ca:N ratios were achieved with the background fertilisation plus nitrapyrin and urea or ammonium nitrate. The system cannot hold onto nutrients, nitrogen in particular, applied in excess of the harmonic stoichiometry.

Optimizing Nitrogen Sources in Top Dressing for Wheat: Field Study on Growth, Yield, and Ammonia Volatilization.

In alkaline calcareous soils, ammonia volatilization is the primary nitrogen (N) loss process, resulting in the reduced N use efficiency of crops. This study aimed at assessing the impact of different N sources for top dressing on ammonia volatilization, as well as their effects on wheat growth and yield over two years. In each year, half of the recommended N was applied as a basal dose using diammonium phosphate (DAP) and urea. The remaining half was top-dressed 35 days after sowing with various sources: prilled urea (PU), granular urea (GU), ammonium sulfate (AS), and calcium ammonium nitrate (CAN) in the first year; PU, urea coated with a urease inhibitor from 20 g (VnU-20) and 40 g (VnU-40) leaves of Vachellia nilotica, biochar-coated urea (BU), and urease inhibitor paraphenylenediamine-coated urea (PPDU) in the second year. Ammonia volatilization losses were tracked for up to 12 weeks from sowing. Ammonia losses from basal-applied N remained consistent in both years, comprising around 4% of the applied N. In the first year, top-dressed AS resulted in the highest losses, followed by GU, while losses from urea and CAN were statistically similar. In the second year, coated fertilizers showed lower ammonia losses compared to PU, with VnU-40 displaying the least losses, 48% less than PU. Nitrogen concentration in wheat grain and straw exhibited a negative correlation with ammonia losses. The choice of top-dressed N source influenced tillering, biological, straw, and grain yields of wheat. In the first year, CAN provided maximum yield benefits, and in the second year, VnU-20 exhibited 27% more grain yield than PU. These findings suggest that top dressing with coated urea, especially VnU-20, has the potential to reduce ammonia losses, improve crop nitrogen status, and enhance economic yield compared to other nitrogen sources.

Solvent-free Synthesis of Transition Metals Nanoparticles Decorated Foamy Flakes-like Nitrogen-doped Carbon as Bifunctional-catalyst for High-performance Rechargeable Zn-air Batteries

Transition metal-nitrogen-carbon (M/NC) demonstrates a promising effective electrocatalyst for enhancing oxygen evolution/reduction reactions (OER/ORR). However, synthesizing these catalysts is often complex, time-consuming, and involves hazardous solvents while producing a low yield. This work introduces a versatile, eco-friendly, and straightforward solvent-free method to produce M/NC (M = Co, Ni, and Fe) catalysts in ~3 h using a glucose, urea, and metal nitrate hydrate mixture. The high-yield M/NC catalysts exhibit a porous architecture and uniform distribution of metal nanoparticles within a foaming flakes-like nitrogen-doped carbon matrix. The metal nanoparticles are wrapped with protective nitrogen-doped carbon layers, producing stable active sites. Possessing these unique properties, the obtained M/NC catalysts show high-performance and stable bifunctional OER/ORR. As the best result, Co/NC presents an OER/ORR potential difference (ΔE) of 0.78 V and retains 96% and 89% of its OER and ORR performance after a 10 h stability test. In practical application, the Co/NC-based Zn-air battery depicts a high power density of 184 mW cm−2 and good rechargeability of up to 120 h, outperforming the battery with noble metal-based catalysts. This work sheds light on the versatile, eco-friendly, and scalable synthesis of M/NC catalysts while presenting a strategy to accelerate the generation of inexpensive and highly effective bifunctional OER/ORR catalysts.

Evaluation of canine training aids containment for homemade explosive and components by headspace analysis and canine testing.

While canines are most commonly trained to detect traditional explosives, such as nitroaromatics and smokeless powders, homemade explosives (HMEs), such as fuel-oxidizer mixtures, are arguably a greater threat. As such, it is imperative that canines are sufficiently trained in the detection of such HMEs. The training aid delivery device (TADD) is a primary containment device that has been used to house HMEs and HME components for canine detection training purposes. This research assesses the odor release from HME components, ammonium nitrate (AN), urea nitrate (UN), and potassium chlorate (PC), housed in TADDs. Canine odor recognition tests (ORTs) were used with analytical data to determine the detectability of TADDs containing AN, UN, or PC. Headspace analysis by gas chromatography/mass spectrometry (GC/MS) with solid-phase microextraction (SPME) or online cryotrapping were used to measure ammonia or chlorine, as well as other unwanted odorants, emanating from bulk AN, UN, and PC in TADDs over 28 weeks. The analytical data showed variation in the amount of ammonia and chlorine over time, with ammonia from AN and UN decreasing slowly over time and the abundance of chlorine from PC TADDs dependent on the frequency of exposure to ambient air. Even with these variations in odor abundance, canines previously trained to detect bulk explosive HME components were able to detect all three targets in glass and plastic TADDs for at least 18 months after loading. Detection proficiency ranged from 64% to 100% and was not found to be dependent on either age of material.

Effect of pH, Carbon and Nitrogen Sources on Antibiotic Production by Actinomycetes Isolates from River Tana and Lake Elementaita, Kenya

The escalating concern over antibiotic resistance and its profound impact on public health have underscored the urgent need to explore alternative reservoirs of antimicrobial agents. In this regard, Actinomycetes have emerged as a compelling area of investigation due to their remarkable capacity to produce bioactive compounds. Therefore, this study sought to investigate the influence of pH and various carbon and nitrogen sources on the antibacterial activity of Actinomycetes isolates collected from Lake Elementaita and River Tana. By examining the effects of these factors, we aimed to gain insights into the optimization of growth conditions and nutrient availability to enhance the production of bioactive compounds with potent antibacterial properties. The Actinomycetes isolates used in this study were from Lake Elementaita and River Tana, known for their diverse ecological characteristics and potential as sources of bioactive compounds. The isolates were subjected to morphological, biochemical, and molecular techniques to ensure accurate identification. To assess the antibacterial activity of the Actinomycetes isolates, they were tested against E. coli using the agar well diffusion method. The independent variables examined in this study were pH levels (4, 7, and 9) as well as different carbon sources (fructose and sucrose) and nitrogen sources (urea and sodium nitrate). The diameter of the inhibition zones served as the dependent variable. The data collected on the effects of pH and nutrients on the inhibition zones of Actinomycetes isolates were subjected to statistical analysis. One-way ANOVA was performed to assess significant differences in antibacterial activity among the isolates under different carbon and nitrogen preference. Mean values were compared using the LSD test at a significance level (α) of 0.05. Furthermore, the Kruskal-Wallis test was utilized to analyze the pH preferences of the Actinomycetes isolates at a significance level (α) of 0.05. The results showed that pH significantly influenced the bioactivity of the Actinomycetes isolates, with pH 7 exhibiting the highest inhibition zones against E. coli. The isolates displayed varied antibacterial activities depending on the carbon and nitrogen sources provided. Sucrose was the most preferred carbon source, followed by fructose, while urea was the preferred nitrogen source, followed by sodium nitrate. The study concluded that pH and nutrient availability play crucial roles in determining the antibacterial activity of Actinomycetes isolates. Other than contributing to our in-depth understanding of the factors influencing the antimicrobial potential of Actinomycetes, the results of this study highlight the importance of optimizing growth conditions and nutrient availability to enhance the production of bioactive compounds with potent antibacterial properties. Further investigations and exploration of Actinomycetes from diverse environments are recommended to discover new bioactive molecules for combating antibiotic resistance.

Selecting bacteria for in-depth self-healing of concrete at both room and low temperature

The large-scale application of microbial self-healing techniques of concrete faces serious challenges from low temperature in high-cold regions and oxygen availability in the cracks. In this study, we focus on the temperature sensitivity and oxygen dependence of microbial self-healing techniques of concrete and select bacteria from the cold-resistant facultative anaerobes through microbial growth, mineralization and healing tests with the most frequently used Sporosarcina pasteurii as control group. The results show the cold-resistant bacteria, Brevibacterium frigoritolerans A779 and A793 have the capability of growing at low temperature compared with S. pasteurii fwzy14. S. pasteurii fwzy14 has the best capability of inducing calcite precipitation at room temperature but its precipitation rate decreases dramatically at low temperature; B. frigoritolerans A779 has the approximate capability with S. pasteurii fwzy14 at low temperature with urea and calcium nitrate as calcium carbonate precursor, which makes it a potential candidate for the in-depth self-healing of concrete in a broad temperature range. Consistent with the results of bacterial growth and mineralization tests, bacterial healing tests show that cold-resistant B. frigoritolerans A779 can not only heal the outer part of the cracks but also heal the inner part better than S. pasteurii fwzy14 at low temperature. Therefore, a plan containing both S. pasteurii fwzy14 and B. frigoritolerans A779 is proposed for in-depth self-healing of concrete at both room and low temperature.